Photographic products and processes



United States Patent 3,326,681 PHOTOGRAPHIC PRODUCTS AND PROCESSES Vivian K. Walworth, Concord, Mass, assignmto Polaroid Corporation, Cambridge, Mass, a corporation of Delaware No Drawing. Filed Aug. 30, 1963, Ser. No. 305,857

8 Claims. (Cl. 96-3) The present invention relates to photography and, more particularly, to photographic products and processes.

As has been extensively reported in the literature pertaining to photography, photosensitive silver halide emulsions, particularly photosensitive gelatino silver halide emulsions, have a tendency to lose sensitivity and to become spontaneously developable without exposure to light. In general, this phenomenon chartcterized as fog is usually ascribed to be the effect of prolonged ripening during fabrication of the emulsion, prolonged storage, especially at elevated temperatures and humidities, and/ or prolonged photographic developement techniques. The quantity of fog is apparently dependent both on the emulsion and the conditions of development, in combination.

Various and sundry procedures and additives have been disclosed in the art to provide an increase in the stability of photosensitive silver halide emulsions, by reduction in the tendency of the photosensitive composition to fog. Many of the stabilizing techniques, and the specific photographic antifoggant, or stabilizing, organic and inorganic compounds heretofore provided for use in photography, have exhibited the singular disadvantage in that they decrease senstivity and/or contrast of the emulsion formulation, especially with regard to emulsions which are optically sensitized to specified regions of the spectrum and are particularly adapted for use in color photography. These disadvantages are especially prevalent when many of the prior art antifoggants have been incorporated in emulsion formulations which retain color image-forming components therein, or in close proximity thereto.

Accordingly, it is a primary object of the present invention to provide novel photographic film units and processes utilizing same.

Another object of the present invention is to provide novel photosensitive elements, comprising not less than one silver halide emulsion, possessing increased speed and improved stability.

A further object of the present invention is to provide novel compositions, processes and products for obtaining silver, monochromatic and multichromatic images by photographic diffusion transfer processes which exhibit increased transfer image densities and improved high lights and light steps.

A still further object of the present invention is to provide compounds which are not only excellent stabilizers or antifogging agents for light-sensitive silver halide emulsions, but, in addition, have the faculty of performing this function without lowering the sensitivity of the emulsion with which they are associated and without reducing the sensitivity of the emulsion to light of longer wave lengths attributable to the presence of optical sensitizing dyes.

A still further object of the present invention is to provide stabilized light-sensitive silver halide emulsions, especially silver halide emulsions exhibiting increased stability against the effects of dry and moist heat.

A still further object of the present invention is to provide novel photographic elements, comprising not less than one silver halide emulsion having associated therewith not less than one contiguous layer containing specified color image-forming components, which exhibit increased stability against the effects of dry and moist heat.

A still further object of the present invention is to provide novel photographic elements, comprising not less than one silver halide emulsion having associated therewith not less than one contiguous layer containing specified color image-forming components, particularly adapted for employment in multichromatic photographic transfer processes, employing integral multilayer photosensitive elements, to provide improved color separation.

A still further object of the present invention is to provide novel photographic elements, comprising not less than one silver halide emulsion having associated therewith not less than one contiguous layer containing specified color image-forming components, which exhibit excellent stability without detachable loss in sensitivity of the emulsion to light of longer wave lengths attributable to the incorporation of optical sensitizing dyes therein.

A still further object of the present invention is to provide methods particularly adapted to prepare stabilized photosensitive silver halide emulsions.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the process involving the several steps and the relation and order of one or more of such steps with respect to each of the others, and the product possessing the features, properties and the relation of elements which are exemplified in the following detailed disclosure, and the scope of the application of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description.

In the prior art, US. Patent No. 2,131,038, issued Sept. 27, 1938, discloses the employment of certain cycloammonium quaternary salts, that is, N-alkyl substituted azoles containing an oxygen, sulfur or selenium atom as a component of the azole ring, as photographic antifogging agents, however, with the admonition that the dis closed agents exert varying degrees of emulsion desensitization.

It has now been unexpectedly discovered that certain cycloammonium quaternary salts, that is, N-carboxyalkyl and N-sulfoalkyl substituted azoles containing an oxygen, sulfur or selenium atom as a component of the azole ring, when incorporated in a photosensitive film unit, provide stability to, and inhibition of, the fogging characteristics of the film units silver halide emulsions, substantially without a reduction in the contrast or speed of the emulsion, and especially without lowering the sensitivity of the emulsion to light of longer wave lengths attributable to the presence of optical (spectral) sensitizing dyes, and in the presence or absence of photographic color imageforming components.

The preferred cycloammonium quaternary salts employed in accordance with the instant disclosure may be represented by the formula:

The aromatic ring system of the formula may contain the substituents usual in the art, for example, substituents such as lower alkyl, lower alkoxy, phenyl, benzyl, chloro, bromo, iodo, amino, hydroxyl, fused benzene ring,-etc., radicals.

As examples of preferred acyclic groups of the formula, mention may be made of lower alkyl groups comprising from 1 to 4 carbon atoms such as methyl, ethyl, isopropyl, etc., and, as exmaples of preferred cyclic groups, mention may be of aromatic radicals of the henzene series such as a phenyl group.

The anion, represented by the designation Z in the formula, comprises those anionic acid radicals customary in the art, for example, chloride, bromide, iodide, ptoluenesulfate, acetate, propionate, cyanate, perchlorate, nitrate, sulfate, etc.

As specific examples of compounds within the preceding generic formulae, mention may be made of:

\g Br 3H2 IO2H 3-carboxymethyl-2-methyl-benzothiazolium bromide H C-CH: \e Br N Hz 102E 3-carboxymethyl-2-methyl-benzoselenazolium bromide H CCHa Er N fls SOQH 2-methy1-3-('y-sulfopropyl)-benzose1enaz0lium bromide 3-carboxymethyl-5-c'hloro-2-methy1-benz0thiazolium bromide SOaH fi-methoxy-fz-methyl-B- fi-sulfobutyl) -benzoselenazoliurn bromide CO2H 3-(fi-carboxyethyl)2-metl1yl-benzoxazolium iodide COH3 COzH

2,5,6-trimethyl3- (1Soarboxyethyl) -benzoxazolium iodide to the emulsion at any stage during its manufacture and/or during photographic processing of same. The addition, therefore, may be made before, during or after the addition of the soluble silver salt to the soluble halide salt in the presence of a suitable colloid such as gelatin, polyvinyl alcohol, etc., and/ or as a coating final just prior to the coating of the emulsion or a supporting member.

It will be recognized that the agents employed in accordance with the present invention may also be used in combination with additional known antifoggants and stabilizers and, where desired, may be included in the processing composition employed for the development, etc., of a photoexposed silver halide emulsion.

In general, the optimum concentration of the agent to be employed should be determined empirically for each specific photographic system. However, it has been experimentally determined that, in general, the preferred concentration falls within the range of about 0.005 to 5.0 milligrams per millimole of silver halide present in the silver halide emulsion, depending upon the fogging characteristics of the silver halide emulsion to be stabilized.

Although concentrations in excess of the first-mentioned range may be employed, increasing the concentration beyond the designated limits generally provides no additional beneficial results. Conversely, concentrations below that of the designated range, however, merely decrease stabilization below the effective level generally sought but do not obliterate obtaining beneficial stabilization results. Where desired, however, substantial quantities of the agent may be employed without introducing serious desensitizing effects.

It has now been further found that the aforementioned stabilizing effects on the photosensitive silver halide emulsion, provided by the employment of stated compounds, in the concentrations stated, may be obtained without lowering the sensitivity of the emulsion with which it is associated and/or without reducing the sensitivity of the emulsion to light of longer wave lengths attributable to the presence of optical (spectral) sensitizing dyes, when such emulsion is employed in a photographic film unit cific examples employing Z-methylbenzothiazole methiodide, Z-methylbenzothiazole ethiodide, benzothiazole ethiodide, and benzothiazole methiodide have been incorporated, in the table, for the purpose of providing comparative data. Analogous results were also achieved with respect to Examples 1 to 4.

Fresh After 1 week at Difference Concentra- 120" F. Compound tion. mg./g.

silver Dmax. Fog Dmax. Fog Dmax. Fog

3-carboxymethyl-2anethylbeuzothiazolium bromid 1.10 .06 1.10 .06 0 0 H-earboxymeth methylbonzoselenazo mide 10 0.92 .02 0. 9G 16 04 +.14 2-methyl-3-( l-sullobutyl)benzoselenazolium bromide 10 0.86 10 0. 02 .10 06 0 3-carboxyethyl-2-methylbenzoselenazolium bromide l0 1. 58 .06 1.76 .22 18 -[-.12 2-methylbenzothiazole methiodid 10 1. 38 0.38 1. 06 0. 4O 32 02 2-mcthylbenzothiazole ethiodide 100 0.60 0.14 0.50 0.10 10 04 Benzothiazole ethiodide 10 0.98 0.14 0.82 0.18 16 04 Benzothiazole methiodide 10 1. 0. 18 1.12 0.23 18 05 which set out representative products and processes, and which, however, is intended to be illustrative and not of limiting effect.

Example 1 11.5 g. of a silver iodobromide emulsion containing approximately 12% silver and 9% gelatine was combined with 12 cc. of distilled water. A 2 cc. solution of each of the antifoggants designated below was added to individual emulsion dispersions. 1.5 cc. of 10% saponin and 1.5 cc. of 10% Alkagel (trade name of Amalgamated Chemical Corp, Philadelphia, Pennsylvania, for a sodium amide sulfonate) were then added to each dispersion. The dispersion was stirred for 5 minutes at 38 C. and coated on a subcoated cellulose acetate film base.

The film unit was then exposed in a standard sensitometer and developed for 1% minutes in Dektol (trade name of Eastman Kodak Company, Rochester, N.Y., for a photographic developing solution).

Example 2 The procedure of Example 1 was repeated with the exception that the film unit was stored for 1 week at a temperature of 120 F. prior to exposure and development.

Example 3 The procedure of Example 1 was repeated with the exception that the dispersion was coated on the exposed surface of a dye-containing layer prepared by coating a subcoated cellulose acetate film base coated with sufficient 2- (p- [2,5 '-dihydroxyphenethyl] -phenylazo -4-isopropoxy-l-naphthol, dispersed in a 4% solution of gelatin, to give a coverage of 100 to 110 mgs. per square foot.

Example 4 The procedure of Example 3 was repeated with the exception that the film unit was stored for 1 week at a temperature of 120 F. prior to exposure in the sensitometer and development.

Example 5 The procedure of Example 3 was repeated with the exception that 2 mgs. of l,1'-diethyl-3,3-bis-(fl-carboxyethyl) 5,5-dichloro-benzimidazolecarbocyanine betaine was included in the silver iodobromide dispersion.

Example 6 The procedure of Example 5 was repeated with the exception that the film unit was subjected to storage for 1 week at a temperature of 120 F. prior to exposure and development.

The indicated antifoggants employed and the results obtained in Examples 5 and 6 are set forth below in tabular form, in the interest of clarity and brevity. Spe- Dye developers, as noted above, are compounds which contain, in the same molecule, both the chromophoric system of a dye and also a silver halide developing function. By a silver halide developing function is meant a grouping adapted to develop exposed silver halide. A preferred silver halide development function is a hydroquinonyl group. Other suitable developing functions include ortho-dihydroxyphenyl and orthoand para-amino substituted hydroxyphenyl groups. In general, the development function includes a benzenoid developing function, that is, an aromatic developing group which forms qinonoid or quinone substances when oxidized.

An extensive compilation of such compuonds is set forth in US. Patent No. 2,983,606, issued May 9, 1961, and, in particular, in the various US. patents and copending applications incorporated by reference therein.

In general, the preferred dye developers comprise monoazo and anthraquinone dyes which possess one or two hydroquinonyl groups attached to the dyes auxochromophoric system by means of a conjugation interrupting divalent group such as, for example, an alkylene group.

It will be recognized that although the beneficial results of the instant invention are, in particular, detailed hereinafter in terms of the preferred diffusion transfer color photographic processes and products particularly adapted for use therein, the concepts of the present invention are also applicable to conventionally processed film of both color and silver types, diffusion transfer processes for the formation of silver transfer images and monochromatic and multichromatic transfer processes employing varied and sundry color image-forming components such as those detailed hereinafter.

In diffusion transfer processes, for the formation of positive silver images, a latent image contained in an exposed photosensitive silver halide emulsion is developed and almost concurrently therewith a soluble silver complex is obtained by reaction of a silver halide solvent with the unexposed and undeveloped silver halide of said emulsion. Preferably, the photosensitive silver halide emulsion is developed with a processing composition in a viscous condition which is spread between the photo sensitive element comprising the silver halide emulsion and a print-receiving element comprising a suitable silver precipitating layer. The processing composition effects development of the latent image in the emulsion and substantially contemporaneous therewith forms a soluble silver complex, for example, a thiosulfate or thiocyanate, with undeveloped silver halide. This soluble silver complex is, at least in part, transported in the direction of the print-receiving element and the silver thereof is largely precipitated in the silver precipitating layer of said element to form a positive image therein.

Additive color reproduction may be produced by exposing a photosensitive silver halide emulsion through an additive color screen having filter media or screen elements each of an individual additive color, such as red or blue or green, and by viewing the reversed or positive silver image, formed by the aforementioned transfer to a transparent print-receiving element, through the same or a similar screen which is suitably registered with the re versed positive image carried by the print-receiving layer.

US. Patents Nos. 2,647,049, issued July 2 8, 1953; 2,661,293, issued Dec. 1, 1953; 2,698,244, issued Dec. 28, 1954; 2,698,798, issued Ian. 4, 1955; 2,802,735, issued Aug. 13, 1957; all to Edwin H. Land, disclose subtractive color diffusion transfer processes wherein color coupling techniques are utilized which comprise, at least in part, reacting one or more developing agents and one or more color formers to provide a positive color image on a superposed image-receiving layer. US. Patent No. 3,019,- 124, issued Jan. 30, 1962, discloses the manufacture of photographic color screen elements; and US. Patents Nos. 2,968,554, issued Jan. 17, 1961 and 2,983,606, issued May 9, 1961 disclose diffusion transfer processes wherein a color screen element is utilized to provide a multicolor positive image to a superposed image-receiving layer. US. Patent No. 2,774,668, issued Dec. 18, 1956, the copending US. application of Edwin H. Land and Howard G. Rogers, Ser. No. 565,135, filed Feb. 13, 1956 and the previously cited US. Patent No. 2,983,606 disclose diffusion t-ransfer processes wherein complete dyes are utilized to provide a positive color image to a superposed image-receiving layer.

As disclosed in the aforementioned U.S. Patent No. 2,983,606, a photosenstive element containing a dye developer and a silver halide emulsion is exposed and wetted by a liquid processing composition, for example, by immersion, coating, spraying, flowing, etc., in the dark, and the exposed photosensitive element is superposed prior to, during, or after wetting, on a sheetlike support element which may be utilized as an image-receiving element. In a preferred embodiment, the liquid processing composition is applied to the photosensitive element in a substantially uniform layer as the photosensitive ele ment is brought into superposed relationship with the image-receiving layer. The liquid processing composition permeates the emulsion to initiate development. The dye developer is immobilized or precipitated in exposed areas as a consequence of the development. This immobilization is apparently, at least in part, due to a change in the solubility characteristics of the dye developer upon oxidation and especially as regards its solubility in alkaline solutions. It may also be due in part to a tanning effect on the emulsion by oxidized developing agent, and in part to a localized exhaustion of alkali as a result of development. In unexposed and partially exposed areas of the emulsion, the dye developer is unreacted and diffusible and thus provides an imagewise distribution of unoxidized dye developer dissolved in the liquid processing composition, as a function of the point-to-point degree of exposure of the silver halide emulsion. At least part of this imagewise distribution of unoxidized dye developer is transferred, by imbibition, to a superposed image-receiving layer or element. Under certain conditions, the layer of liquid processing composition may be utilized as the image-receiving layer. The image-receiving element receives a depthwise diffusion, from the developed emulsion, of unoxidized dye developer without appreciably disturbing the imagewise distribution thereof to provide the reversed or positive color image of the developed image. The image-receiving element may contain agents adapted to mordant or otherwise fix the diffused, unoxidized dye developer. If the color of the transferred dye developer is affected by changes in the pH of the image-receiving element, this pH may be adjusted to provide a pH affording the desired color. The desired positive image is revealed by stripping the image-receiving layer from the photosensitive element at the end of a suitable imbibition period.

Multicolor images may be obtained using color imageforming components such as, for example, the previously mentioned dye developers, in diffusion transfer processes by several techniques. One such technique contemplates the use of a photosensitive silver halide stratum comprising at least two sets of selectively sensitizied minute photosensitive elements arranged in the form of a photosensitive screen. Transfer processes of this type are disclosed in the previously noted US. Patent No. 2,983,606. In such an embodiment, each of the minute photosensitive elements has associated therewith an appropriate dye developer in or behind the silver halide emulsion portion. In general, a suitable photosensitive screen, prepared in accordance with the disclosures of said patent, comprises minute red-sensitized emulsion elements, minute greensensitized emulsion elements and minute blue-sensitized emulsion elements arranged in side-by-side relationship in a screen pattern and having associated therewith, respectively, a cyan dye developer, a magenta dye developer and a yellow dye developer.

Another process for obtaining multicolor transfer images utilizing dye developers employs an integral multilayer photosensitve element, such as is disclosed in the aforementioned copending US. application of Edwin H. Land and Howard G. Rogers, Ser. No. 565,135, filed Feb. 13, 1956, wherein at least two selectively sensitized photosensitive strata are superposed on a single support and are processed, simultaneously and without'separation, with a single, common image-receiving layer. A suitable arrangement of this type comprises a support carrying a red-sensitive silver halide emulsion stratum, a green-sensitive silver halide emulsion stratum and a blue-sensitive silver halide emulsion stratum, said emulsions having associated therewith, respectively, for example, a cyan dye developer, a magenta dye developer and a yellow dye developer. The dye developer may be utilized in the silver halide emulsion layer, for example, in the form of particles, or it may be employed as a layer behind the appropriate silver halide emulsion strata. 'Each set of silver halide emulsion and associated-dye developer strata may be separated from other sets by suitable interlayers, for example, by a layer of gelatin or polyvinyl alcohol. In certain instances, it may be desirable to incorporate a yellow filter in front of the green-sensitive emulsion and such yellow filter may be incorporated in an interlayer. However, where desirable, ayellow dye developer of the appropriate spectral characteristics and present in a state capable of functioning as a yellow filter may be employed. In such instances, a separate yellow filter may be omitted.

In accordance with the preceding description, a photosensitive element was prepared by coating a gelatin-coated film base with s-uflicient 2-(p-[2,5-dihydroxyphenethyl]- phenylazo)-4-isopropoxy-l-naphthol, dispersed in a 4% solution of gelatin, to give a coverage of to mgs. per square foot. After this coating had dried, a silver iodobromide emulsion, prepared according to the procedure of Example 1 and containing 12% silver in a 9% solution of gelatin and 1,1'-diethyl-3,3-bis-(fl-carboxyethyl -5 ,5 '-dichloro-benzimidazolecarbocyanine betaine was applied. The photosensitive elements were then exposed and processed by spreading the aqueous liquid processing composition comprising:

Water cc 100 Sodium hydroxide grams 5.17 Hydroxyethyl cellulose do 4.03 Sodium thiosulfate do 1.15 Benzotriazole do 2.3 Benzyl-ot-picolinium bromide do 2.3 4'-methyl phenyl hydroquinone do 0.2

between said photosensitive element and an image-receiving element comprising a sheet of cellulose acetate s-ubcoated baryta paper having coated thereon a mixture of polyvinyl alcohol and poly-4-vinylpyridine, as said elements were brought into superposed relationship. After an imbibition period of one minute, the image-receiving element was separated and revealed a monochromatic reversed magenta dye image of the photosensitive elements exposure response.

Multicolor diffusion transfer processes were conducted employing the previously identified agents, the image-receiving element and processing composition set forth in the preceding example, and multi-layer photosensitive elements prepared in the manner disclosed in the aforementioned copending US. application Ser. No. 565,135. In general, the photosensitive elements comprised a support carrying a red-sensitive silver halide emulsion stratum, a green-sensitive silver halide emulsion stratum and a bluesensitive silver halide emulsion stratum; said emulsions having dispersed in water-immiscible organic solvents and contained in separate alkali-permeable gelatin layers behind them, respectively, a cyan dye developer, a magenta dye developer and a yellow dye developer. The particular dye developers employed in the photosensitive elements were 1,4-bis-(a-methyl-fi-hydroquinonylethylamino)-5,8- dihydroxyanthraquinone (a cyan dye developer); 2-(p- [2,5'-dihydroxyphenethyl] phenylazo)-4-isopropoxy-1- naphthol a magenta dye developer); and 1-phenyl-3-nhexyl-carbxamido-4-(p-[hydroquinonylethyl] phenylazo)-5-pyrazolone (a yellow dye developer). The lastmentioned cyan dye developer is disclosed in the copending U.S. application of Blout et al. Ser. No. 233,461, filed Oct. 26, 1962, and the last-mentioned yellow and magenta dye developers are disclosed in the copending US. application of Blout et al. Ser. No. 145,978, filed Oct. 18, 1961.

A further technique for obtaining multicolor images employs a plurality of photosensitive elements associated with an appropriate number of image-receiving elements and adapted to be treated with one or more liquid processing compositions, the appropriate dye developers being incorporated in the photosensitized elements. Examples of fil-m processes of this type are disclosed in US. Patent No. 2,647,049, issued July 28, 1953.

The preceding color image-forming components, that is, dye developers, are preferably selected for their ability to provide colors that are useful in carrying out subtractive color photography, i.e., cyan, magenta and yellow. It should be noted that it is within the scope of this invention to use mixtures of dye developers, for example, to obtain a desired color, e.g., black. Thus it is to be understood that the expression color as used herein is intended to include the use of a plurality of colors to obtain black, as well as the use of a single black dye developer.

The dye developers employed in the processes of this invention may be incorporated in the photosensitive elements in, on, or behind the respective silver halide emulsion. As illustrated, the dye developer may, for example, be in a coating or layer behind the silver halide emulsion and such a layer of dye developer may be applied by the use of a coating solution containing about 0.5 to 8%, by Weight, of the respective dye developer.

The liquid processing composition referred to for effecting monochromatic and multicolor transfer processes comprises at least an aqueous solution of an alkaline compound, for example, diethylamine, sodium hydroxide or sodium carbonate and possesses a pH in excess of 12 preferably. If the liquid processing composition is to be applied to the emulsion by being spread thereon, preferably in a relatively thin uniform layer, it includes a viscosityincreasing compound constituting a film-formaing material of the type which, when said composition is spread and dried, forms a relatively firm and relatively stable film. A preferred film-forming material is a high molecular weight polymer such as a polymeric, water-soluble ether which is inert to an alkaline solution such as, for example, a hydroxyethyl cellulose or sodium carboxymethyl cellulose. Other film-forming materials or thickening agents whose ability to increase viscosity is substantially unalfected if left in solution for a long period of time may also be used. The film-forming material is preferably contained in the processing composition in suitable quantities to impart to said composition a viscosity in excess of 1,000 centipoises at a temperature of approximately 24 C. and preferably of the order of 1,000 to 200,000 centipoises at said temperature. Illustrations of suitable liquid processing compositions may be found in the several patents and copending applications herein mentioned and also in examples herein given. Under certain circumstances, it may be desirable to apply a liquid processing composition to the photosensitive element prior to exposure, in accordance with the technique described in US. Patent No. 3,087,816, issued Apr. 30, 1963.

It will be noted that the liquid processing composition employed may contain an auxiliary or accelerating developing agent, such as p-methy-laminophenol, 2,4-diaminophenol, p-benzylaminophenol, hydroquinone, toluhydroquinone, phenylhydroquinone, 4'-methylphenylhydroquinone, etc. It is also contemplated to employ a plurality of auxiliary or accelerating developing agents, such as a 3-pyrazolidone developing agent and a benzenoid developing agent, as disclosed in US. Patent No. 3,039,869, issued June 19, 1962. As examples of suitable combinations of auxiliary developing agents, mention may be made of 1-phenyl-3-pyrazolidone in combination with p-benzylaminophenol and l-phenyl-S-pyrazolidone in combination with 2,5-bis-ethyleneimino-hydroquinone. Such auxiliary developing agents may be employed in the liquid processing composition or they may be initially incorporated, at least in part, in the silver halide emulsion strata or the strata containing the dye developers. It may be noted that at least a portion of the dye developer oxidized during development may be oxidized and immobilized as a result of a reaction, e.g., an energy-transfer reaction, with the oxidation product of an oxidized auxiliary developing agent, the latter developing agent being oxidized by the development of exposed silverhalide. Such a reaction of oxidized developing agent with unoxidized dye developer would regenerate the auxiliary developing agent for further reaction with the exposed silver halide.

In addition, development may be effected in the presence of an onium compound, particularly a quaternary ammonium compound, in accordance with the processes disclosed in the copending US. application of Milton Green and Howard G. Rogers, Ser. No. 50,861, filed Aug. 22, 1960.

In products employed in the diffusion transfer processes of this invention, it is preferable to expose from the emulsion side. It is, therefore, desirable to hold the photosensitive element and the image-receiving element together at one end thereof by suitable fastening means in such manner that the photosensitive element and the image-receiving element may be spread apart from their superposed processing position during exposure. A cemera apparatus suitable for processing roll film of the type just mentioned is provided by the Polaroid Land Camera, sold by Polaroid Corporation, Cambridge, Mass, or similar camera structure such, for example, as the camera forming the subject matter of US. Patent No. 2,435,717. Camera apparatus of this type permits successive exposure of individual frames of the photosensitive element, from the emulsion side thereof, as well as individual processing of an exposed frame by bringing said exposed frame into superposed relation with a predetermined portion of the image-receiving element, while drawing these portions of the film assembly between a pair of pressure rollers, and require a container associated there with to effect the spreading of the processing liquid released by rupture of said container, between and in contact with the exposed photosensitive frame and the predetermined registered area of the image-receiving element.

It will be apparent that the relative proportions of the agents of the processing compositions set forth may be altered to suit the requirements of the operator. Thus,'it is within the scope of this invention to modify the herein described developing compositions by the substitution of preservatives, alkalis, silver halide solvents, etc., other than those specifically mentioned, provided that the pH of the composition is initially in excess of at least 10, for most favorable results, and most preferably in excess of 12. When desirable, it is also contemplated to include, in the developing composition, components such as restrainers, accelerators, etc. Similarly, the concentration of developing agent may be varied over a wide range and when desirable the developing agent may be disposed in the photosensitive element, prior to the exposure of the emulsion, in a separate permeable layer of the photosensitive element and/ or in the photosensitive emulsion.

The support layers referred to may comprise any of the various types of conventional rigid or flexible supports, for example, glass, paper, metal, and polymeric films of both synthetic types and those derived from naturally occurring products. Suitable materials include paper; aluminum; polymethacrylic acid, methyl and ethyl esters; vinyl chloride polymers; polyvinyl acetal; polyamides such as nylon; polyesters such as polymeric films derived from ethylene glycol terephthalic acid; and cellulose derivatives such as cellulose acetate, tria-cetate, nitrate, propionate, butyrate, acetate-propionate, or acetate-butyrate.

It will be understood that silver halides of varying halide concentrations may be advantageously employed and that the silver halide emulsions employed may be chemically sensitized by any of the accepted procedures. For example, the emulsions may be chemically sensitized with sulfur compounds such as sodium thiosulfate or thiourea; with reducing substances such as stannous chloride; with salts of noble metals such as gold, rhodium and platinum; with amines and polyamines; with quaternary ammonium compounds such as a-picolinium bromide, etc., and with polyethylene glycols and derivatives of same.

The emulsions may also be optically sensitized with cyanine and merocyanine dyes and, where desired, additional antifoggants, restrainers, accelerators, preservatives, and/ or coating aids may be included in the composition of the emulsion.

The image-receiving element, for use in monochromatic and multichromatic subtractive color processes, comprises an image-receiving layer of opaque or transparent material which is liquid permeable and dyeable from alkaline solutions and which for purposes of simplicity may comprise a single sheet of permeable material, for example, paper. This element, however, may comprise a support upon which at least one liquid-permeable and dyeable layer is mounted. The support layer may have a water-impermeable subcoat over which the stratum of permeable and dyeable material is applied. In certain instances, the dyeable layer may comprise a layer of liquid processing composition which is adapted to remain adhered to the support layer upon stripping.

It will be apparent that, by appropriate selection of the image-receiving element from among suitable known opaque and transparent materials, it is possible to obtain either a colored positive reflection print or a colored positive transparency.

As examples of additional image-receiving materials, for use in the last-mentioned transfer processes, mention may be made of nylon such as N-methoxyrnethyl polyhexamethylene adipamide; partially hydrolyzed polyvinyl acetate; polyvinyl alcohol with or without plasticizers; baryta paper, i.e., a support having a baryta coating thereon; cellulose acetate with filler as, for example, one-half cellulose acetate and one-half oleic acid; gelatin; and other materials of a similar nature. Preferred materials comprise polyvinyl alcohol or gelatin containing a dye mordant such as poly-4-vinylpyridine, as disclosed in the copending U.S. application of Howard C. Hass, Ser. No. 50,848, filed Aug. 22, 1960.

Particularly desired image-receiving elements comprise a flexible laminate which includes, in sequence, a support a polymeric acid layer, an optional permeable polymeric timing layer, and a solution dyeable polymeric imagereceiving layer as disclosed in the copending US. application of Edwin H. Land, Ser. No. 234,864, filed Nov. 1,1962.

While a rupturable container provides a convenient means for spreading a liquid processing composition between layers of a film unit whereby to permit the processing to be carried out within a camera apparatus, the

practices of this invention may be otherwise effected. For example, a photosensitive element, after exposure in suitable apparatus and while preventing further exposure thereafter to actinic light, may be removed from such apparatus and permeated with the liquid processing composition, as by coating the composition on said photosensitive element or otherwise wetting said element with the composition, following which the permeated, exposed photosensitive element, still, without additional exposure to actinic light, is brought. into contact with the imagereceiving element for image formation in the manner heretofore described. s

In all examples of this specification, percentages of components are given by weight unless otherwise indicated.

Throughout the specification and appended claims, the expression positive image has been used. This expression should not be interpreted in a restrictive sense since it is used primarily for purposes. of illustration, in that it defines the image produced on the image-carrying layer as being reversed, in the positive-negative sense, with respect to the image in thephotosensitive element. As an example of an alternative meaning for positive image, assume that the photosensitive element is exposed to actinic light through a negative transparency. In this case, the latent image in the photosensitive element will be a positive and the image produced on the image-carrying layer will be a negative. The expression positive image is intended to cover such an image produced on the image-carrying layer.

Throughout the specification and claims, the expression superposing has been used. This expression is intended to cover the arrangement of two layers in overlying relation to each other either in face-to-face contact or in separated condition and including between them at least one layer or stratum of a material which may be a viscous liquid.

Since certain changes may be made in the above products, compositions and processes without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A photographic product which comprises, in combination, a plurality of layers including a support, a silver halide emulsion located in a layer on said support, said silver halide emulsion having associated therewith an antifoggant of the formula:

emulsion also having associated therewith, in a layer on the same side of said support, a dye which is a silver halide developing agent.

2. A photographic product as defined in claim 1, wherein said antifoggant is located in said layer containing said silver halide emulsion.

3. A photographic product as defined in claim 1, wherein said dye is selected from the group consisting an anthraquinone and azo dyes which are silver halide developing agents.

4. A photographic product as defined in claim 3, wherein said radical is a hyd-roquinonyl silver halide developing radical.

5. A photographic product as defined in claim 1 wherein said compound is selected from the group consisting of 3-carboxymethyl-2-methy1 benzothiazole, 3-carboxymethyl-2-methyl benzolselenazole, 2-methyl-3-( -sulfopropyl -benzolselenazole, 2-methyl-3-(6-sulfobutyl -benzolselenazole, 3-carboxymethyl-S-chloro-2-methyl-benzothiazole, and 3-(fl-carboxyethyl)-2-methyl-benzoselenazole.

6. In a process of forming diffusion transfer images in color which comprises the steps of developing an exposed photosensitive element comprising a plurality of layers including a silver halide emulsion layer, at least one of said layers containing a dye, which dye is a silver halide developing agent, by contacting said element with an aqueous alkaline solution, immobilizing said dye in the exposed areas of said element, as a result of development, forming thereby an imagewise distribution of mobile dye, as a function of the point-to-point degree of exposure of said element, and transferring, by imbibition, at least a portion of said imagewise distribution of mobile dye to a superposed image receiving layer to provide thereto a positive dye image, the improvement which comprises at least one of said plurality of layers including an antifoggant of the formula:

7. A process as defined in claim 6, wherein said antifoggant is located in a layer containing a silver halide emulsion.

8. In a multicolor difiusion transfer process which comprises the steps of developing an exposed photosensitive element comprising a plurality of layers including blue-sensitive, green-sensitive and red-sensitive silver halide gelatin emulsion layers mounted on a common support, said blue-sensitive, green-sensitive and redsensitive silver halide gelatin emulsion layers having positioned contiguous, respectively, yellow, magenta and cyan dyes, each of said yellow, magenta and cyan dyes being a silver halide developing agent, by permeating said photosensitive element with an aqueous alkaline processing composition, immobilizing said yellow, magenta and cyan dyes in exposed areas, as a result of development, forming thereby an imagewise distribution of mobile yellow, magenta and cyan dye, as a function of the point-to-point degree of exposure of said element, and transferring, by imbibition, at least a portion of each of said imagewise distributions of mobile dye to a superposed image-receiving layer to provide thereto a multicolor positive dye image, the improvement which comprises at least one of said plurality of layers including an antifoggant of the formula:

wherein A represents an acid group selected from the group consisting of carboxylic and sulfonic acid groups; n represents a positive integer from 1 to 4, inclusive; :R represents a monovalent radical selected from the group consisting of an alkyl group containing from 1 to 4 carbon atoms, a phenyl group, and hydrogen; X comprises the nonrnetallic atoms necessary to complete an aromatic ring system of the benzene series; Y is selected from the group consisting of oxygen, sulfur and selenium atoms; and Z represents an anion.

References Cited UNITED STATES PATENTS 2,131,038 9/1938 Brooker et al. 96109 2,912,329 11/1959 Jones et al. 96109 2,983,606 5/1961 Rogers 9629 3,189,453 6/1965 Herz et al 96109 FOREIGN PATENTS 587,434 4/1947 Great Britain.

NORMAN G. TORCHIN, Primary Examiner, 

8. IN A MULTICOLOR DIFFUSION TRANSFER PROCESS WHICH COMPRISES THE STEPS OF DEVELOPING AN EXPOSED PHOTOSENSITIVE ELEMENT COMPRISING A PLURALITY OF LAYERS INCLUDING BLUE-SENSITIVE, GREEN-SENSTIVE AND RED-SENSITIVE SILVER HALIDE GELATIN EMULSION LAYERS MOUNTED ON A COMMON, SUPPORT, SAID BLUE-SENITIVE, GREEN-SENSITIVE AND REDSENSITIVE SILVER HALIDE GELATIN EMULSION LAYERS HAVING POSITIONED CONTIGUOUS, RESPECTIVELY, YELLOW, MAGENTA AND CYAN DYES, EACH OF SAID YELLOW, MAGENTA AND CYAN DYES BEING A SILVER HALIDE DEVELOPING AGENT, BY PERMEATING SAID PHOTOSENSITIVE ELEMENT WITH AN AQUEOUS ALKALINE PROCESSING COMPOSITION, IMMOBILIZING SAID YELLOW, MAGENTA AND CYAN DYES IN EXPOSED AREAS, AS A RESULT OF DEVELOPMENT, FORMING THEREBY AN IMAGEWISE DISTRIBUTION OF MOBILE YELLOW, MAGENTA AND CYAN DYE, AS A FUNCTION OF THE POINT-TO-POINT DEGREE OF EXPOSURE OF SAID ELEMENT, AND TRANSFERRING, BY IMBIBITION, AT LEAST A PORTION OF EACH OF SAID IMAGEWISE DISTRIBUTIONS OF MOBILE DYE TO A SUPERPOSED IMAGE-RECEIVING LAYER TO PROVIDE THERETO A MULTICOLOR POSITIVE DYE IMAGE, THE IMPROVEMENT WHICH COMPRISES AT LEAST ONE OF SAID PLURALITY OF LAYERS INCLUDING AN ANTIFOGGANT OF THE FORMULA: 